Organopolysiloxanes having polyester groups have been known for a long time. For example, U.S. Pat. No. 5,051,489 describes hydrophobic silicone polyester waxes that are obtained by esterification of the silanol groups of siloxanediols with dicarboxylic acids and fatty acids. These waxes are polyesters with a blockwise structure of dialcohols and dicarboxylic acids in which the polysiloxane takes on the function of the dialcohol.
U.S. Pat. No. 5,385,730 discloses mixtures consisting of a low-viscosity silicone oil and a polyester-radical-carrying polysiloxane with a block structure whose polyester radicals are obtained by lactone ring-opening. As well as the polyester radicals, these polysiloxanes can also carry long-chain alkyl radicals. These polysiloxanes are hydrophobic polysiloxanes that can be used as polishes.
Japanese Patent No. B-3046340 describes polyesters that are obtained by the reaction of terminal aliphatic hydroxyl-group-containing siloxanediols and dicarboxylic acids, such as adipic acid, and subsequent reaction with monocarboxylic acids, e.g., also hydroxystearic acid. The silicone polyesters are recommended for use in cosmetics.
U.S. Pat. No. 5,411,729 describes, inter alia, silicone polyesters which are obtained by reacting siloxanes carrying lateral or terminal polyether radicals having free OH groups with dicarboxylic acids and polyhydroxy compounds, such as glycerol, and optionally with a monofunctional carboxylic acid. The compounds are used as conditioning agents for hair. U.S. Pat. No. 5,475,125 discloses amphiphilic silicone polyesters that are obtained by reacting a comb-like polyethersiloxane having free OH groups with a dicarboxylic acid and a fatty alcohol ethoxylate. These amphiphilic silicone polyesters are recommended as emulsifiers for silicone oil-in-water emulsions.
From the description of the prior art it is clear that silicone polyesters of varying structure are known.
It is possible to differentiate between two basic types of polyester. Firstly those which are obtained by polycondensation of polyalcohols with dicarboxylic acids, and those which are obtained by self-condensation of hydroxy-functional carboxylic acids or by ring-opening reaction of corresponding lactones.
The first-mentioned type has a block structure if the polyalcohol is a diol. Here, the polysiloxane can take on the function of the diol, as described in U.S. Pat. No. 5,051,489 or Japanese Patent No. B-3046340. The siloxanediol can carry silanol-like OH groups, which leads to readily hydrolyzable Si—O—C bonds, or hydroxyalkyl groups, which produce hydrolysis-resistant Si—C bonds.
However, the siloxane can also carry more than 2 OH groups, as describe in U.S. Pat. No. 5,475,125. A disadvantage of the silicone polyesters prepared in this way is that the dicarboxylic acid used can act as a bridge between two silicone polyethers and triggers crosslinking reactions which are difficult to control and which may lead to complete gelation of the product.
U.S. Pat. No. 5,411,729 also discloses silicone polyesters which, as well as the polyhydroxy-functional siloxane, additionally contain an organic polyhydroxy compound as a building block. However, in this case too, crosslinking reactions are to be expected.
Silicone polyesters can be prepared in a more controlled manner by ring-opening reactions of lactones with hydroxy-functional siloxanes, see, for example, U.S. Pat. No. 5,385,730. In this way, crosslinking reactions can be completely avoided.
In principle, polyester siloxanes can be divided into amphiphilic and nonamphiphilic types. Siloxanes, which carry only polyester radicals, are usually hydrophobic and do not exhibit interface activity between a hydrophilic and a hydrophobic phase. Polyester siloxanes that also carry hydrophilic groups, such as, for example, polyether radicals are, by contrast, interface-active and can be used, for example, as emulsifiers. This is disclosed, for example, in U.S. Pat. Nos. 5,411,729 and 5,475,125.
The use of amphiphilically modified polysiloxanes, in particular polyether-modified polysiloxanes, as emulsifiers and dispersing agents has been known for a long time. The use of interface-active silicone polyethers in emulsifier systems is described in detail, for example, in U.S. Pat. No. 4,988,504. Polysiloxane compounds are proposed which consist of
a) units of the formulaR2SiO2/2, wherein                R=hydrogen or a substituted or unsubstituted hydrocarbon radical having 1 to 12 carbon atoms,        
b) units of the formulaRR1SiO2/2, wherein                R1=polyalkylene ether of the formula—R3a—(OR2)n—OR4, in which        R2=—CH2CH2—,        R3=substituted or unsubstituted alkylene group having 1 to 20 carbon atoms,        R4=R,        n has a value from 5 to 20, and        a is 0 or 1, and        
c) end members of the siloxane chain,
where the molecular weight of component a) should be about 25,000 to 35,000.
These emulsifiers with lateral polyoxyalkylene groups should bring about improved properties for antiperspirant sticks with regard to stability and low wax content.
European Patent B-0 407 089 relates to a transparent water-in-silicone oil emulsion, suitable for external application to mammallain skin or hair, comprising, in addition to water:    i. 1 to 50% by weight of a volatile polydimethylsiloxane;    ii. 0.1 to 20% by weight of a silicone surfactant ingredient comprising a polymer of dimethylpolysiloxane with polyoxyethylene and/or polyoxypropylene sidechains with a molecular weight of from 10,000 to 50,000 and the structural formula:
    iii. 1 to 50% by weight of a transparency-imparting agent, which is at least one polyhydric alcohol.
European Patent B-0 176 844 discloses the use of polysiloxanes with polyether and long-chain alkyl radicals added on in a comb-like manner as emulsifiers for the preparation of W/O emulsions, the oily phase of which consists of silicone oil, or comprises this. European Patent A-0 819 426 describes the use of terminally modified polyethersiloxanes as emulsifiers in W/O emulsions.
The disadvantage of prior art polyether-modified polysiloxanes described here is, however, that when the polyether-moified polysiloxanes are used as emulsifiers in W/O emulsions, undesirably high emulsion viscosities, especially in the case of emulsions with a high water phase content, are achieved.